The invention relates to an article of integrally-merged, hard and soft polyvinyl chloride (hereinafter PVC) and, more particularly, an article having a wall with a first, continuous region of PVC of lower hardness than at least one, second, smaller region of PVC of greater hardness than the first region integrally merged therewith.
German utility model patent publication No. 77 16 857 describes an air-intake tube for the internal-combustion engine of a motor vehicle which has axially-successive wall regions of alternately greater and lower hardness. This results in good shape stability and isolation of the vibrations produced by the motor. Fabrication requires manually cementing together ring moldings for the succeeding regions, however, which is not easily acceptable economically. The vibrations during use can, further, combine with the vacuum in the interior of the tube during use to break fragments out of the harder wall regions which can seriously damage the engine. Such damage has been repeatedly observed in overhauling motor vehicles equipped with such air-intake tubes.